1. Field of the Invention
The present invention generally relates to systems for tying down and securing payloads carried by vehicles, aircraft, watercraft, and the like, or mounted to walls or other stationary structures, and more particularly concerns systems utilizing tracks having slidable carriages that are capable of securely holding payloads of various sizes, shapes and weights, and that may be factory installed or installed as after-market accessories.
2. Description of the Prior Art
The array of systems that may be used to tie-down and secure payloads carried by vehicles, aircraft, watercraft, and stationary structures includes those systems having tracks upon which carriages slide, with means to temporarily secure the carriages at various positions along said tracks, and having means to attach straps, ropes or cords between the carriages to secure payloads.
The tracks of such systems may be rectangular in cross-section and formed of relatively thin metal stock bent to define a channel, such as described by U.S. Pat. Nos. 3,713,616, and 3,698,678, or formed of solid rectangular stock in which a channel has been extruded, such as described by U.S. Pat. No. 4,850,769. In addition, the tracks of such systems may be tubular, having a relatively thin wall circular cross section, such as described by U.S. Pat. No. 3,698,678, or, may be an irregular shape in which a channel has been extruded, such as those described by U.S. Pat. Nos. 4,020,770 and 4,085,684. In addition, the internal channel of the track may be of rectangular cross-section with an opening to a side of the track, circular in cross-section with an opening to a side of the track, or may be of oblong cross-section with an opening to a side of the track.
Unfortunately, the tracks of such existing systems may have insufficient structural strength to withstand the forces produced when a heavy payload is secured, with the carriages acting to pull out of relatively thin walled tracks, to distort the tracks to the point of inoperativeness, or to cause such stresses upon the tracks that the structural integrity of the tracks is compromised by way of fissures or cracks, eventually causing track breakage.
The carriages, the means to temporarily secure the carriages at various positions along the tracks, and the means to attach straps, ropes or cords between the carriages to secure payloads may be integrated into a single unit having relatively complex internal structure, such as described by U.S. Pat. Nos. 3,212,457, 4,020,770, 4,085,684, and 4,850,769. In such systems, the cost of production of the relatively complex units is significant, and the chances of mechanical breakdown or malfunction is increased. Other systems have the carriages, the means to temporarily secure the carriages, and the means to attach straps, ropes or cords between the carriages in the form of multiple distinct elements, such as described by U.S. Pat. Nos. 3,698,678 and 3,713,616.
Despite the availability of such systems, there exists a need in the art for a payload tie-down system that is capable of use as both a factory installed system and an after-market accessory for a wide variety of vehicles, aircraft, watercraft and stationary structures, is capable of repeated and long use to securely hold large and heavy payloads of various sizes and shapes, yet has a minimum number of structurally simple components, is easily used and maintained, and is inexpensive to produce.